Production of secondary metabolites in regenerated Southern wormwood (Artemisia abrotanum L.) under various experimental conditions

Abstract

Southern wormwood (Artemisia abrotanum L.) is a widely distributed plant from the Asteraceae family that produces a variety of volatile oils. This research explores the production of secondary metabolites in Southern wormwood by extracting the essential oils from control specimens grown in the greenhouse compared with regenerated wormwood in culture or sterile soil. Analysis of the essential oils was performed by gas chromatography-mass spectrometry (GC/MS). Control plants grown in soil were similar to regenerated plants grown in soil. For regenerated plants grown in culture, the largest differences in production were increases in nordavanone (fivefold over control) and (E)-2-decanal (sixfold over control). In vitro cultures were also tested with heat-treated Gram-positive (Bacillus subtilis) or Gram-negative (Escherichia coli) bacterial cultures. Regenerated plants grown in the presence of 1% (v/v) E. coli differed from all other culture treatments in highly elevated levels of trans-alpha-bergamotene, alpha-acoradiene, and gleenol with large reductions in davanone and 8-cedren-13-ol. Regenerated plants grown in culture without bacterial treatment showed higher levels of nordavanone and (E)-2-decanal versus plants in culture treated with bacteria. When comparing classes of compounds, the major observation was a large increase in sesquiterpene hydrocarbons and a large decrease in tetrahydrofuran for cultures treated with 1% (v/v) E. coli relative to all other treatments. While each treatment presented distinct profiles of secondary metabolites, the present data suggested that Southern wormwood showed the largest response to being treated with 1% (v/v) E. coli.